Adding directional link widget

IPython/html/static/widgets/js/widget_link.js

@@ -42,7 +42,46 b' define(['
             this.updating = false;
         },
     });
+
+    var DirectionalLinkModel = widget.WidgetModel.extend({
+        initialize: function() {
+            this.on("change", this.update_bindings, this);
+            this.on("destroy", function() {
+                if (this.source) {
+                    this.source[0].off("change:" + this.source[1], null, this);
+                }
+            }, this);
+        },
+        update_bindings: function() {
+            if (this.source) {
+                this.source[0].off("change:" + this.source[1], null, this);
+            }
+            this.source = this.get("source");
+			if (this.source) {
+                this.source[0].on("change:" + this.source[1], function() { this.update_value(this.source); }, this);
+                this.update_value(this.source);
+            }
+        },
+        update_value: function(elt) {
+            if (this.updating) {return;}
+            var model = elt[0];
+            var attr = elt[1];
+            var new_value = model.get(attr);
+            this.updating = true;
+            _.each(this.get("targets"),
+                   function(element, index, list) {
+						if (element[0]) {
+							element[0].set(element[1], new_value);
+							element[0].save_changes();
+                        }
+                   }, this);
+            this.updating = false;
+        },
+    });
+
+
     return {
         "LinkModel": LinkModel,
+        "DirectionalLinkModel": DirectionalLinkModel,
     }
 });

IPython/html/widgets/__init__.py

@@ -10,7 +10,7 b' from .widget_selection import RadioButtons, ToggleButtons, Dropdown, Select'
 from .widget_selectioncontainer import Tab, Accordion
 from .widget_string import HTML, Latex, Text, Textarea
 from .interaction import interact, interactive, fixed, interact_manual
-from .widget_link import Link, link
+from .widget_link import Link, link, DirectionalLink, dlink
 
 # Deprecated classes
 from .widget_bool import CheckboxWidget, ToggleButtonWidget

IPython/html/widgets/widget_link.py

@@ -15,7 +15,7 b' click events on the button and trigger backend code when the clicks are fired.'
 # Imports
 #-----------------------------------------------------------------------------
 from .widget import Widget
-from IPython.utils.traitlets import Unicode, Tuple
+from IPython.utils.traitlets import Unicode, Tuple, Any
 
 #-----------------------------------------------------------------------------
 # Classes
@@ -31,5 +31,24 b' class Link(Widget):'
         kwargs['widgets'] = widgets
         super(Link, self).__init__(**kwargs)
 
+
 def link(*args):
     return Link(widgets=args)
+
+
+class DirectionalLink(Widget):
+    """Directional Link Widget"""
+    _model_name = Unicode('DirectionalLinkModel', sync=True)
+    targets = Any(sync=True)
+    source = Tuple(sync=True)
+
+    # Does not quite behave like other widgets but reproduces
+    # the behavior of IPython.utils.traitlets.directional_link
+    def __init__(self, source, targets=(), **kwargs):
+        kwargs['source'] = source
+        kwargs['targets'] = targets
+        super(DirectionalLink, self).__init__(**kwargs)
+
+
+def dlink(source, *targets):
+    return DirectionalLink(source, targets)